I drained her to negative ST in one hit. So, she has no ST. She has a weapon, MoD, with less base stats,75, and less x than mine, 3300. Yet, on top of the flash, she does 3.7M damage with no ST. Please explain this.

Because B Ark is not using a shield of capacity so its not returning that damage, times the first blood lust hit. If he was and that character always got hit in range round like maidens then you would probably be seeing higher damage than 6 mill.

It is the BL. The first hit adds an additional 150% to the damage. This would put it around 6 mil and you have no damage reduction. SoC returned damage is affected by all the regular things of melee damage. VA, BL, and the special effects of the weapon being used.

and yes BL is supposed to affect SoC granted damage. All the SoC does is increase the next hit by the flash amount. This damage is then susceptible to BL, VA, other SoC reduction, AC and any special abilities of the weapon being used. So the SoC flash will give 20% VA with a morg or double damage vs AS and disruption on a MoD.